Printing units of an offset printing press include a form cylinder, a transfer cylinder, an inking unit, and preferentially, a dampening unit. On the form cylinder of such a printing unit, at least one print form is positioned, which can be designed as a printing plate, which is why form cylinders are also called plate cylinders. On the transfer cylinder of such a printing unit, at least one transfer form is positioned, which can be designed as a blanket and which is why transfer cylinders are also called blanket cylinders. The inking unit of such a printing unit serves for applying printing ink, and the dampening unit of such a printing unit that may be present serves for applying dampening solution onto the or each print form positioned on the form cylinder. Starting out from the or each print form positioned on the form cylinder, the printing ink is transferred onto a substrate to be printed via the or each transfer form positioned on the transfer cylinder, wherein the substrate to be printed is moved through a nip that is positioned between the transfer cylinder and an impression cylinder. The impression cylinder can be a satellite cylinder or also a transfer cylinder of another printing unit. During printing, so-called blanket build-up, which can consist of ink remains and parts of the substrate to be printed can form on the or each transfer form. Such a blanket build-up impairs the achievable print quality and can result in web tears during the printing of a web-like substrate. For this reason it is known from practice to clean the or each transfer form that is positioned on a transfer cylinder before the start of a new print production.
During the printing of particularly high-quality print products, such as for example when printing magazines or catalogues, blanket washing can take place also during the production. In the process, a cleaning device is engaged with a rotating transfer cylinder at full or at reduced production speed and a washing agent is applied onto the transfer cylinder, namely onto the or each transfer form arranged on the transfer cylinder.
From the prior art, a multitude of different cleaning devices for printing presses are known, which serve for cleaning a rotating, cylindrical surface of a printing press cylinder, or a printing press roller, or a surface of a print form or transfer form arranged on a cylinder surface, with which in particular blanket washing can therefore be carried out. Such cleaning devices include a housing, wherein preferentially multiple cleaning devices, namely a washing device and a separate drying device, are accommodated. The washing device serves for washing the respective surface to be cleaned with the help of a liquid washing agent. The drying device serves for drying the cleaned surface.
From U.S. Pat. No. 3,390,993A and from U.S. Pat. No. 4,015,307A, such cleaning apparatuses each with a washing device and a drying device are known, which are accommodated by a housing. Furthermore, it is known that either the washing device or the drying device is engaged with the surface to be cleaned in order to remove and transport away contaminations from the surface to be cleaned in a first cleaning step by way of the washing device, and in order to dry the cleaned surface in a subsequent second cleaning step.
For cleaning a rotating, print-related surface within a printing unit of a printing press, highly solvent-containing liquid washing agents are employed according to practice. Such highly solvent-containing washing agents can on the one hand attack the surface to be cleaned. However, on the other hand the handling of such highly solvent-containing washing agents requires great care because of their health risk potential.